Nuclear small-subunit rDNA sequences from three species of Ballia (Ceramiales, Rhodophyta) native to southern Australia have been investigated, initially to assess the tribal placement of the genus within the Ceramiaceae. In distance and parsimony analyses, however, Ballia callitricha was strongly positioned in the ‘two-cap-layered pit-plug assemblage’ of the Florideo-phyceae as a distinct lineage, sister to the Acrochaetiales, Batrachospermales, Nemaliales and Palmariales. These taxa are only remotely related to the florideophyte ‘membrane-only pit-plug lineage’ that includes the Ceramiales. As B. callitricha is the type species of the genus Ballia and is distinct in anatomical and molecular features from all recognized orders in the two-cap-layer lineage, a new order and family, Balliales H.-G. Choi, Kraft & G.W. Saunders ord. nov. and Balliaceae H.-G. Choi, Kraft & G.W. Saunders fam. nov., are proposed to accommodate B. callitricha, B. pennoides, B. sertularioides, and a new species, B. nana Kraft & G.W. Saunders sp. nov., the latter known from a single collection in the Melbourne region of southeast Australia. Ballia ballioides and B. mariana, on the other hand, were solidly allied to the membrane-only taxa, although their position within this lineage, particularly with reference to the Ceramiales, was equivocal in our analyses. Nevertheless, these two species are clearly distinct from B. callitricha in morphological and molecular characters, and both are transferred to the new genus Inkyuleea H.-G. Choi, Kraft & G.W. Saunders, as I. ballioides (Sonder) H.-G. Choi, Kraft & G.W. Saunders comb. nov. (the type species) and I. mariana (Harvey) H.-G. Choi, Kraft & G.W. Saunders comb. nov. Inkyuleea differs in a number of reproductive characteristics from existing members of the Ceramiales, the possible significance of which is discussed.
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